1. Field of the Invention
The present invention relates to a multi-plate clutch system including: a clutch outer connected to an input member; a clutch inner connected to an output member; multiple driving friction plates engaged with the clutch outer in such a way as to be movable in an axial direction, and to be unrotatable relative to the clutch outer; multiple driven friction plates interleaved with the driving friction plates, the driven friction plates being engaged with the clutch inner in such a way as to be movable in the axial direction and to be unrotatable relative to the clutch inner; a pressure plate movable in the axial direction in order to cause the driving friction plates and the driven friction plates to frictionally engage with each other by bringing the driving friction plates and the driven friction plates into pressure contact with each other; a clutch spring for biasing the pressure plate in a direction in which the pressure plate brings the driving friction plates and the driven friction plates into pressure contact with each other; and at least one of an assist mechanism and a slipper mechanism, the assist mechanism being configured to increase a pressure-contact force of the pressure plate when acceleration torque is changed, the slipper mechanism being configured to decrease the pressure-contact force of the pressure plate when deceleration torque is changed.
2. Description of Background Art
Japanese Patent Application No. 2008-38954 discloses a multi-clutch system, which is designed to increase a pressure-contact force between driving friction plates and driven friction plates in such a way that: when acceleration torque is changed, an assist mechanism retracts a clutch inner; and thereby, in addition to a biasing force exerted on the clutch inner by a clutch spring, the retracting force is caused to work on the pressure plate.
In the multi-plate clutch system disclosed by Japanese Patent Application No. 2008-38954, however, the pressure plate is unitarily formed with the clutch inner. For this reason, the retracting force exerted on the clutch inner from the assist mechanism works on the pressure plate as well, and the pressure-contact force between the driving friction plates and the driven friction plates accordingly increases. At this time, the biasing force produced by the clutch spring and the retracting force produced by the assist mechanism additively work at almost the same timing. This may make the pressure plate move abruptly. As a result, the clutch connection may be rough.